1. Field of the Invention
The present invention relates to a technique which facilitates changing energy usage in a given environment in response to an external request. More specifically, the present invention relates to a technique for using a power-line phase-cut signaling technique to change energy usage for one or more devices sharing a common power signal.
2. Related Art
The amount of energy which is used by a power grid can fluctuate greatly over time. This can be a problem, because there may not exist sufficient power-generation capacity to handle peak energy requirements. Utility companies typically use emergency-demand energy management techniques to avoid system overload and rolling blackouts during times of peak energy usage. For example, utility companies and state independent service operators (ISOs) can send a demand-response (DR) signal via the Internet or phone lines during peak periods to request that customers temporarily shed energy load until the peak periods have passed.
While sending such a signal to customers involves low infrastructure cost, automatically forwarding this signal to “sheddable” loads at each customer site can involve considerable cost. For instance, in most buildings, existing building automation and energy-control systems lack cannot shed individual loads or categories of loads, and adding such capabilities typically involves expensive rewiring. Alternative technologies, such as wireless mesh networks that use cellular and radio-frequency signals, can be used, but these alternative technologies typically require expensive hardware to be added to every device that receives the signal.
Hence, what is needed is a method and an apparatus for efficiently distributing requests to change energy usage to individual devices without the problems listed above.